ASA 127th Meeting M.I.T. 1994 June 6-10

2aPP22. A wavelet representation of acoustic information in the auditory
cortex.

Steven P. Dear

James A. Simmons

Dept. of Neurosci., Box 1953, Brown Univ., Providence, RI 02912

A previous study demonstrated that a subpopulation of cortical neurons
comprised a multiresolution decomposition of target range information in the
big brown bat [Dear et al., Nature 364, 620--622 (1993)]. Given the strong
relationship between a multiresolution decomposition and wavelets, it was
wondered if acoustic information is represented as wavelets in the auditory
cortex. Here, the existence of Daubechies wavelets in the auditory cortex in
response to multiharmonic FM sweeps simulating the type of signals used by the
big brown bat for echolocation is reported. The Daubechies wavelets exist as
continuous analog voltages that appear to be evoked by a local ensemble of
cortical neurons. The wavelets are sensitive to manipulations of multiple
synthetic echoes and suggest an orthogonal representation of acoustic echo
information in the auditory cortex. [Work supported by NSF.]